Pineapple jam: Grate the pineapple or blend with a food processor. Transfer the shredded pineapple and its juice along with cinnamon stick and cloves into a heavy-bottom pan. Cook over medium heat and stir occasionally until the liquid is gone.

Cookie dough: Using an electric mixer, cream the butter and margarine together for 1 minute on medium speed. Add sugar and beat for another minute just to combine.

Add egg yolk and mix briefly for 10 seconds. Then sieve the custard powder and flour into the bowl. Mix until it forms a uniform dough. If the dough feels sticky, add a little more flour (1 teaspoon at a time). Add butter if it's dry. It should be easily formed into a ball without crumbling or sticking.

Press the ball in between your palms to make a thin disk. Place 1 piece of pineapple jam on the center. Wrap it and pinch the edges closed. Roll it back into a ball and place on a baking sheet lined with parchment paper. Repeat with the rest.

Bake in a preheated oven at 300°F (150°C) for 30 minutes. Let cool completely on a wire rack before applying egg wash for the second bake.

Brush each of the cookies with the egg wash. After the first coat has set, apply a second coat. These multiple coats will conceal any visible cracks and create a shiny yellow crust.